1. Field of the Invention
The present invention relates to a maintenance system for a machine tool including driver mechanisms such as a spindle unit, a tool clamp unit and an automatic tool changer and a controller for controlling operations of the driver mechanisms, the maintenance system being adapted to perform a management operation on the operating life expectancies of the driver mechanisms.
2. Description of the Prior Art
One exemplary machine tool of the aforesaid type is illustrated in FIG. 10. The machine tool 21 is a so-called vertical machining center. The machine tool 21 illustrated in FIG. 10 includes: a bed 22; a column 23 provided upright on the bed 22; a spindle unit 24 rotatably supporting a spindle 25 and supported by the column 23 in a vertically movable manner; a table 26 provided below the spindle unit 24 on the bed 22; a tool magazine 40 provided on the left side of the spindle unit 24; an automatic tool changer 42 provided at a lower end of the tool magazine 40 for exchanging a tool T attached to the spindle 25 and a tool T stored in a retainer pot 41 of the tool magazine 40; a clamp unit 57 as shown in FIG. 11 for fixing the tool T to a front end (lower end) of the spindle 25; and a numerical controller 80 as shown in FIG. 13 for controlling the respective components of the machine tool 21.
As shown in FIG. 11, the spindle unit 24 includes the spindle 25, a housing 50 rotatably supporting the spindle 25 via a bearing 51, a cover 52 provided at a front end of the housing 50, and a driving motor (not shown) for rotatively driving the spindle 25. A taper hole 25a for receiving the tool T is formed in the front end of the spindle 25 (as seen in the direction of an arrow D).
As shown in FIG. 11, the clamp unit 57 includes a collet 53 provided in the spindle 25 for holding a pull stud (holder portion) Ta of the tool T fitted in the taper hole 25a of the spindle 25, a push-pull rod 54 engaged with the collet 53, a driving rod 60 coupled to the push-pull rod 54, coned disc springs 61 for biasing the driving rod 60 in the direction of an arrow E, and a hydraulic cylinder (not shown) for moving the driving rod 60 in the direction of the arrow D.
When a hydraulic pressure is supplied to the hydraulic cylinder (not shown), the clamp unit 57 moves the driving rod 60 in the direction of the arrow D against a biasing force of the coned disc springs 61, whereby the push-pull rod 54 and the collet 53 are moved in the direction of the arrow D to open a front end of the collet 53 which holds the pull stud Ta of the tool T. Thus, the tool T can be withdrawn from the taper hole 25a of the spindle 25. Where the tool T is fitted in the taper hole 25a of the spindle 25 in this state, the pull stud Ta of the tool T is inserted in the collet 53. When the supply of the hydraulic pressure to the hydraulic cylinder (not shown) is stopped in this state, the driving rod 60 is moved in the direction of the arrow E by the biasing force of the coned disc springs 61 to close the collet 53, whereby the tool T attached to the spindle 25 is held by the collet 53 with the pull stud Ta thereof inserted in the direction of the arrow E.
As shown in FIG. 12, the automatic tool changer 42 includes: a rotation shaft 43 provided parallel to the spindle 25; a changer arm 44 fixed to a lower end of the rotation shaft 43; roller-shaped cam followers 70 provided around an outer circumference of a middle portion of the rotation shaft 43 at a predetermined angular interval for rotating the rotation shaft 43 about an axis thereof; a lever-shaped cam follower 71 provided in engagement with the rotation shaft 43 below the cam followers 70 for moving the rotation shaft 43 along the axis thereof; a roller gear cam 72 having guide grooves formed in an outer circumference thereof for engagement with the cam followers 70, and a guide groove formed in a side face thereof for engagement with the cam follower 71; a gear 76 integrally fixed to the roller gear cam 72; and a motor 73 for generating a rotative driving force which is transmitted to the gear 76 via transmission gears 74, 75 and the like. The cam followers 70 each include an engagement roller rotatably supported by a bearing for engagement with the guide groove formed in the outer circumference of the roller gear cam 72. The cam follower 71 includes an engagement roller rotatably supported by a bearing for engagement with the guide groove formed in the side face of the roller gear cam 72.
In the automatic tool changer 42, the rotative driving force is transmitted from the motor 73 to the roller gear cam 72 via the gears 74, 75, 76 and the like to rotate the roller gear cam 72 about the axis thereof, whereby the rotation shaft 43 is rotated about the axis thereof by the action of the cam followers 70 engaged with the roller gear cam 72 and is axially moved by the action of the cam follower 71 engaged with the roller gear cam 72. The action of the rotation shaft 43 causes the changer arm 44 to perform a tool changing operation.
As shown in FIG. 13, the numerical controller 80 includes a CNC 81, a PLC 82, an input/output interface 83 and the like, and is connected to an external control circuit 84 via the input/output interface 83. The control circuit 84 is connected to the spindle unit 24, the automatic tool changer 42 and the clamp unit 57. The CNC 81 executes a machining program stored therein to control basic operations of the machine tool 21 such as axial movements of the spindle unit 24 and the table 26. The PLC 82 includes a spindle controlling section 82a, a clamp controlling section 82b, a changer controlling section 82c and the like, and controls auxiliary operations of the machine tool 21 such as operations of the spindle unit 24, the automatic tool changer 42 and the clamp unit 57 upon reception of commands applied from the CNC 81.
More specifically, the spindle controlling section 82a drives and controls a spindle motor (not shown) upon reception of a rotating command applied from the CNC 81 to rotate the spindle 25 shown in FIG. 11 at a commanded speed in a commanded rotation direction. The clamp controlling section 82b drives the hydraulic cylinder (not shown) of the clamp unit 57 upon reception of a tool clamp command or a tool unclamp command applied from the CNC 81 to clamp or unclamp the tool T attached to the spindle 25. The changer controlling section 82c drives the automatic tool changer 42 upon reception of a tool changing command applied from the CNC 81 to perform the tool changing operation.
As described above, the spindle 25 is rotatably supported by the bearing 51, and the cam followers 70, 71 also employ the bearings. The bearings naturally each have a limited service durability due to the wear and the like of rolling element thereof and, hence, have a finite service life. Further, the clamp unit 57 employs the coned disc springs 61, which naturally have a limited fatigue durability because the coned disc springs 61 are repeatedly subjected to a load and, hence, have a finite service life.
Where the service lives of the bearing 51, the bearings of the cam followers 70, 71 and the coned disc springs 61 end during operation to result in breakage thereof, the time required for recovery from the breakage is prolonged depending on operating conditions thereof at the breakage. Moreover, there is a danger of breakage of other components depending on the conditions of the breakage. The breakage of a greater number of components further prolongs the time required for repair of the components. This disadvantageously reduces the availability of the machine tool. If there are no spare components, the machine tool cannot be repaired until replacement components are delivered. This further reduces the availability of the machine tool. Where spare components are prepared for prevention of such an inconvenience, on the other hand, inventory may disadvantageously be increased to excess.
To cope with this problem, Japanese Unexamined Patent Publication No. 9-292311 (1997) proposes a method for estimating the life expectancy of a rolling bearing which may be employed as the bearing 51 for supporting the spindle 25. With the life expectancy estimating method, the life expectancy of the bearing 51 can be estimated, so that the bearing 51 can systematically be changed before the breakage thereof on the basis of the estimated life expectancy.
However, the life expectancy estimating method is applicable only to a case where the bearing 51 is subjected to a constant load. That is, where the load exerted on the bearing 51 varies from moment to moment as in the machine tool, it is impossible to accurately estimate the life expectancy of the bearing 51.
In most cases, a plurality of machine tools are installed in a plant and, if a life expectancy estimating unit is provided for each of the machine tools for management thereof, management efficiency may be reduced. Further, detection of the end of the service life of some component may be failed, making it impossible to perform an ideal management operation.
As described above, the machine tool generally includes various driver mechanisms which include expendable components with finite service lives, for example, the bearing 51, the bearings of the cam followers 70, 71, the coned disc springs 61 of the clamp unit 57, and a ball screw mechanism. Particularly, the ball screw mechanism requires a longer turnaround time for production thereof, so that a supplier does not always have a stock at the breakage of the ball screw mechanism.
In view of the foregoing, it is an object of the present invention to provide a machine tool maintenance system which is adapted to centrally perform a management operation on the life expectancies of expendable components of driver mechanisms in machine tools installed in a plant for systematic maintenance of the machine tools.
In accordance with a first aspect of the present invention to solve the aforesaid problems, there is provided a machine tool maintenance system, which comprises: a plurality of machine tools each including a plurality of driver mechanisms and a controller for controlling operations of the driver mechanisms; and a management unit connected to the plurality of machine tools; wherein the controller of each of the machine tools comprises a life expectancy determining section for determining the degrees of wear of the respective driver mechanisms on the basis of operating conditions of the respective driver mechanisms; wherein the management unit comprises a data storage section for receiving data indicative of the wear degrees of the respective driver mechanisms determined by the life expectancy determining sections of the respective machine tools and storing the data of the wear degrees for each of the machine tools, and an output section for outputting information on the wear degrees stored in the data storage section.
In the machine tool maintenance system according to the present invention, the wear degrees of the respective driver mechanisms such as a spindle unit and a clamp unit of the machine tool are determined on the basis of the operating conditions of the driver mechanisms by the life expectancy determining section provided in the controller of the machine tool. The data indicative of the wear degrees thus determined is transmitted to the management unit connected to the controller, and stored in the data storage section. At the same time, the information on the wear degrees is outputted by the output section.
In accordance with the invention, the data indicative of the wear degrees of the respective driver mechanisms is transmitted to the management unit, and cumulatively stored in the management unit. Even with the plurality of machine tools, the wear degrees of the driver mechanisms of the respective machine tools can centrally be managed, so that a comprehensive maintenance plan can easily be formulated for the plurality of machine tools. Thus, the availability of the machine tools can effectively be increased.
The life expectancy determining section may be adapted to estimate end-of-life times at which the service lives of the respective driver mechanisms end, on the basis of the wear degrees determined by the life expectancy determining section. The data storage section of the management unit may be adapted to receive data indicative of the wear degrees and the estimated end-of-life times from the life expectancy determining section, and store the data. Further, the output section of the management unit may be adapted to display information on the wear degrees and the estimated end-of-life times stored in the data storage section.
With this arrangement, the end-of-life times of the respective driver mechanisms are estimated by the life expectancy determining section, and the estimated end-of-life times are outputted by the output section of the management unit. Therefore, an operator can easily know the end-of-life times of the respective driver mechanisms on the basis of the output, and systematically perform a maintenance operation in the future.
In accordance with a second aspect of the present invention, there is provided a machine tool maintenance system, which comprises: a plurality of machine tools each including a plurality of driver mechanisms and a controller for controlling operations of the respective driver mechanisms; and a management unit connected to the plurality of machine tools; wherein the management unit comprises a life expectancy determining section for determining the degrees of wear of the respective driver mechanisms on the basis of data indicative of operating conditions of the respective driver mechanisms received from the controller of each of the machine tools, a data storage section for storing data indicative of the wear degrees determined by the life expectancy determining section, and an output section for outputting information on the wear degrees stored in the data storage section.
In the machine tool maintenance system, the wear degrees of the respective driver mechanisms are determined on the basis of the operating conditions of the driver mechanisms by the life expectancy determining section provided in the management unit. The data of the wear degrees thus determined is stored in the data storage section, and the information on the wear degrees is outputted by the output section. Even with the plurality of machine tools, the wear degrees of the driver mechanisms of the respective machine tools can centrally be managed as in the aforesaid case, so that a comprehensive maintenance plan can easily be formulated for the plurality of machine tools. Thus, the availability of the machine tools can effectively be increased.
The life expectancy determining section may be adapted to estimate end-of-life times at which the service lives of the respective driver mechanisms end, on the basis of the wear degrees determined by the life expectancy determining section. The data storage section may be adapted to store data indicative of the wear degrees and the estimated end-of-life times. Further, the output section may be adapted to output information on the wear degrees and the estimated end-of-life times stored in the data storage section.
With this arrangement, the end-of-life times of the respective driver mechanisms are estimated by the life expectancy determining section, and the estimated end-of-life times are outputted by the output section. Therefore, an operator can easily know the end-of-life times of the respective driver mechanisms on the basis of the output, and systematically perform a maintenance operation in the future as in the aforesaid case.
The management unit may include at least one management unit provided on the side of a user of the machine tools and connected to a management unit provided on the side of a supplier of the machine tools via a network. In this case, the supplier side management unit comprises a data storage section for storing data indicative of life expectancies of the respective driver mechanisms received from the user side management unit, and an output section for outputting information on the life expectancies stored in the data storage section.
With this arrangement, the data indicative of the life expectancies of the driver mechanisms of the respective machine tools applied from the user side management unit connected to the machine tools, i.e., the data indicative of the wear degrees where only the wear degrees of the respective driver mechanisms are determined in the user side management unit, or the data indicative of the wear degrees and the estimated end-of-life times where the end-of-life times are estimated in addition to the wear degrees, is transmitted to the supplier side management unit, then cumulatively stored in the storage section, and outputted from the output section. Thus, the machine tool supplier can know the wear degrees and the estimated end-of-life times of the driver mechanisms of the respective machine tools owned by the user, and efficiently prepare replacement components for the driver mechanisms in accordance with the wear degrees and the estimated end-of-life times.
In accordance with a third aspect of the present invention, there is provided a machine tool maintenance system, which comprises: a plurality of machine tools each including a plurality of driver mechanisms and a controller for controlling operations of the respective driver mechanisms; at least one management unit provided on the side of a user of the machine tools and connected to the plurality of machine tools; and a management unit provided on the side of a supplier of the machine tools and connected to the user side management unit; wherein the supplier side management unit comprises a life expectancy determining section for determining the degrees of wear of the respective driver mechanisms on the basis of data indicative of operating conditions of the respective driver mechanisms received from the controller via the user side management unit, a data storage section for storing data indicative of the wear degrees determined by the life expectancy determining section, and an output section for outputting information on the wear degrees stored in the data storage section. The life expectancy determining section may be adapted to determine the wear degrees of the respective driver sections and estimate end-of-life times at which the service lives of the respective driver mechanisms end, on the basis of the determined wear degrees. The data storage section may be adapted to store data indicative of the wear degrees determined by the life expectancy determining section and the estimated end-of-life times. Further, the output section may be adapted to output information on the wear degrees and the estimated end-of-life times stored in the data storage section.
With this arrangement, the machine tool supplier can know the wear degrees and the estimated end-of-life times of the driver mechanisms of the respective machine tools owned by the user, and efficiently prepare replacement components for the driver mechanisms in accordance with the wear degrees and the estimated end-of-life times.